DESCRIPTION (provided by investigator): We propose an initial study to evaluate inhibitory deficits in ADHD adults. We focus on inhibition because it is fundamental to executive functions, which are hypothesized to be deficient in ADHD. Extensive empirical evidence points to deficits of motor output in ADHD children and initial evidence of similar deficits in ADHD adults. Exploration of inhibition deficits in ADHD adults would aid in determining the extent of continuity between the pediatric and adult forms of the disorder. We propose to test 40 well characterized ADHD adults and 40 matched normal controls in tasks measuring three aspects of inhibition (interference control, intentional motor inhibition, and eye movement control) with well delineated cognitive and neurological bases. In addition, we will test subjects in a long vigil involving a Go/No-go version of a Continuous Performance Test in order to assess whether ADHD adults display deficits of sustained attention in intentional motor inhibition. We will collect measures of accuracy and speed in these tasks, supplemented by (a) Lateralized Readiness Potentials (brain event-related potentials [ERPs] reflecting differential preparedness of the motor cortex to make a response with a predesignated vs. the unprepared hand and the timing of initiation of these responses); (b) Inhibition error-related ERPs triggered by the detection of errors and linked to cingulate cortex and supplemental motor areas; and (c) Oculomotor inhibition in delayed and antisaccade tasks, which are controlled by the dorsolateral prefrontal cortex and the frontal eye fields, and an oculomotor Go/No-go task. Several of the brain structures involved in these tasks are intimately involved in executive functions central to ADHD neurocognitive deficits. The proposed research promises to advance current theoretical understanding of executive dysfunction in ADHD. The research would prepare the groundwork for a more extensive future study that would evaluate the effects of pharmacological interventions on inhibition deficits of ADHD adults.